Ontario treated to double dose of mild air, but with a big, chilly interruption
Spring teases this week in southern Ontario, but with some major temperature swings for March break
Early signs of spring will spread across southern Ontario this week as an active pattern builds through the eastern half of North America. That means some impressive milder warm-ups, but also with the chance for some rain, rumbles of thunder, and a major temperature drop in between.
By the weekend, daytime highs could hit the 20-degree mark for the first time this year in Canada!
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First round of warmth spreads into southern Ontario for Monday and Tuesday
A warm front will bring the first spring tease to start out this week in southern Ontario.
We’ll see temperatures rise into the double digits across most regions by the late afternoon hours Monday––away from communities under the control of chilly lake breezes, of course.
Westerly winds will push into the region on Tuesday, meaning milder conditions will prevail across the entire Greater Toronto Area (GTA). Maximum temperatures could climb up to 15°C, marking the warmest day of the year from Windsor to Toronto.
A few locations across extreme southwestern Ontario could make a run at a high temperature of 17°C to 18°C on Tuesday, potentially challenging Canada’s warmest temperature so far in 2025. That title is currently held by Lethbridge, Alta., where the temperature climbed above 17°C on March 1.
Temperatures drop in a hurry by Wednesday but then another warm-up arrives for the weekend
Conditions will remain generally sunny across the region through Tuesday, with increasing clouds ahead of a cold front’s arrival late Tuesday.
Warm-weather lovers beware: This will be a very sharp cold front. Temperatures will rapidly drop below the freezing mark by Tuesday night, with below-seasonal temperatures dominating the region by Wednesday.
Daytime highs are forecast to sit around the freezing mark on Wednesday.
You won’t have to wait long for temperatures to rebound again across southern Ontario. This time however, the warmth won't come with the sunshine.
A developing Colorado low is expected to track into extreme northwestern Ontario by the weekend, dragging a warm front across southern portions of the province.
Combined with the influence of a strong centre of high pressure over the Atlantic Ocean, a sharp southerly flow will develop for a big chunk of Ontario.
As a result, above-seasonal temperatures are likely from Windsor to Moosonee, stretching all across eastern Ontario, as well. We will likely see Canada’s first 20°C of the year by the end of this week.
The threat for showers—and possibly even some rumbles of thunder—will accompany the weekend warmth as it pushes into the region.
Stay with The Weather Network for your latest forecast across Ontario.